Johann Christian Bach, the youngest son of Johann Sebastian, is in various ways an atypical Bach. He was the only one who had a vivid interest in composing operas, which was one of the reasons he moved to Italy. There he converted to the Roman Catholic Church and took a position as organist in Milan. He then moved to London which was one of the main cultural centres in Europe at the time. Stylistically he probably moved further away from his father than any of his brothers. In modern times he is clearly overshadowed by Carl Philipp Emanuel and Wilhelm Friedemann whose works are is much more frequently performed than his. Johann Christian is one of the main representatives of the galant idiom and for many years that militated against performance. This style was considered rather superficial: galant music went in one ear and out the other and made no lasting impression. Slowly that view was reconsidered and that had everything to do with the rise of the use of period instruments.

The sonatas op. 5 are a landmark in music history especially because they had a strong influence on Mozart. On his concert tour across Europe, together with his father Leopold and sister Nannerl, he stayed for some time in London and met Johann Christian. The result was a strong and lasting friendship. Until the end of Bach's life Mozart held him in high esteem. When Bach died Mozart wrote to his father: "What a loss for the world of music!". He arranged three of the sonatas from op. 5, the numbers 2 to 4, as concertos for keyboard, two violins and bass. This is the main reason why this set became Bach's best-known music well before the rest of his oeuvre was taken seriously.

Printed editions with keyboard music were mostly aimed at the fast-growing market of amateurs. That was especially the case in England where domestic music-making at the homes of the bourgeoisie was booming at the time Bach lived in London. He certainly had this kind of player in mind when he composed his sonatas. This was also observed by the music historian Charles Burney, who wrote: "In general, his compositions for the pianoforte are such as ladies can execute with little trouble; and the allegros rather resemble bravura songs than instrumental pieces for the display of great executions". Mention of the pianoforte suggests that Bach's sonatas were conceived for this instrument which was rather new at the time they were published (1766). However, we should not jump to any conclusions from this statement which doesn't specifically refer to the op. 5 set. At that time various instruments coexisted: the harpsichord, the fortepiano and probably also the spinet. For that reason it is impossible to say that a specific instrument is the best medium for these sonatas.

The first of the set includes dynamic markings which reflect the fashion of the time. It suggests the fortepiano, but could also be performed at the harpsichord. From around the middle of the century harpsichords with devices such as machine stops and Venetian swell were built in an attempt to save the harpsichord from being pushed off the music scene. The Sonata No. 5 opens with an allegro assai which is "all noise and technical fireworks", as Sylvia Berry writes in the booklet to the present disc. She continues: "One way composers achieved dynamics at the harpsichord was by simple addition and subtraction: the more notes there are, the louder it is, and vice versa. The first and last movements feature typical 'noise-making' devices in the left hand that were used by many harpsichord composers to create more volume and a fuller texture (...)." The sixth sonata begins with a grave which then turns attacca into a fugue, and this could again suggest the use of the harpsichord. On the other hand, the opening movement of the second sonata, which Berry connects with military music, partly because of the key of D major, comes off particularly well on the fortepiano.

One specific form of fortepiano was the square or table piano which was very popular in England at the time and was produced in large numbers, also because it was relatively cheap. It would have been an interesting option to perform these sonatas on such an instrument. In her liner-notes Berry mentions this option, and adds that this was an instrument for domestic music-making; not for public performances. She states that it is hard to imagine Bach performing exclusively on them when good grand pianos were available. That may be plausible, but the use of the kind of piano Bart van Oort plays here is not very plausible at all. I find it hard to understand why someone as knowledgeable as Van Oort decided to use a copy of a fortepiano by Anton Walter from around 1795. That is not the kind of instrument which was known in England at the time. An opportunity has been missed to perform these sonatas on instruments which were in vogue in Johann Christian's time, be it a harpsichord with dynamic devices or a square piano or even an English grand piano from the 1760s or 1770s.

That is especially regrettable as the performances are excellent. Van Oort is a seasoned interpreter of classical and romantic repertoire on fortepianos, and he takes Johann Christian Bach's music fully seriously. He pays much attention to the different features of the respective sonatas, and his interpretation does justice to the stylistic differences within this set. This is a very fine recording on the fortepiano, and a good alternative to Sophie Yates' performances on the harpsichord (Chandos CHAN0762). However, there is still room for a recording which comes closer to the circumstances under which these sonatas were originally performed.